1. Field of the Invention
The invention relates to a labeling machine, more particularly to a labeling machine that is capable of attaching a label precisely to different sizes of containers.
2. Description of the Related Art
Commodities, such as beverage bottles, drug bottles, containers, and packaging boxes, are generally provided with a label to classify products, to indicate usage and other information, to display the trademark or logo of the manufacturer, etc. With the recent advancement in automation, automated attachment of labels to such commodities has taken the place of manual label attachment, and has become quite popular in the industry.
In a conventional label attaching process, a reel of labels is arranged on a reel supporting plate. A leading edge of the reel is drawn via a driving device to a label applicator plate where the labels are applied to containers being advanced by a container conveyer.
Although the conventional labeling machine can perform automatic label attaching, since the construction thereof is complicated, it cannot be quickly adjusted to adapt to different sizes of containers. The conventional labeling machine generally includes a sensor that generates a signal upon sensing a front end of a container being advanced by a container conveyor, and a label applicator that applies a label to the advancing container a certain period of time or a certain count of digital signals after generation of the signal by the sensor. As the label is preferably attached to the container when a vertical central plane of the container is aligned with the label applicator so that the label can be precisely attached onto the container, as illustrated in FIG. 1, if the containers to be applied with the labels differ in diameter, the labeling machine has to be adjusted so as to ensure the precise attachment of the labels to the containers. For instance, if the labeling machine that is originally used to attach labels to containers with a diameter of 30 mm is now used to attach labels to containers with a diameter of 60 mm, the labeling machine has to be accordingly adjusted so that the label applicator is precisely aligned with the central plane of each container. At present, such an adjustment is still performed manually, in combination with alteration of computer control programs according to size of the containers and rotational speed of the container conveyer, etc., and has to be conducted by technicians or engineers since ordinary workers do not possess the required skill for such complicated adjustment.
Therefore, the main object of the present invention is to provide a labeling machine capable of precise attachment of a label to different sizes of containers.
Accordingly, a labeling machine of this invention includes a motor-driven container conveying unit, a container sensor, an encoder unit, a label applying unit, and a controller. The conveying unit has a feed-in end and a take-out end. The conveying unit is adapted to convey a container from the feed-in end to the take-out end such that a leading edge of the container faces toward the take-out end and such that a trailing edge of the container faces toward the feed-in end. The trailing edge is spaced apart from the leading edge by a distance equal to a diameter of the container. The container sensor is disposed adjacent to the conveying unit between the feed-in and take-out ends. The container sensor generates a first signal upon detection of the leading edge of the container that is being conveyed by the conveying unit, and further generates a second signal upon detection of the trailing edge of the container that is being conveyed by the conveying unit. The encoder unit is associated with the conveying unit, and is operable so as to generate distance information to indicate distance advanced by the leading edge of the container from the container sensor during operation of the conveying unit. The label applying unit includes a label applicator plate disposed adjacent to the conveying unit between the container sensor and the take-out end. The controller is coupled electrically to the encoder unit, the container sensor and the label applying unit. The controller activates the encoder unit upon receipt of the first signal from the container sensor, and determines the diameter of the container that is being advanced by the conveying unit by inspecting the distance information from the encoder unit upon receipt of the second signal from the container sensor. The controller activates the label applying unit so as to be adapted to attach a label to the container being advanced by the conveying unit when the label applicator plate is aligned with a central plane of the container between the leading and trailing edges upon determination from the distance information of the encoder unit that the leading edge of the container has been displaced from the container sensor by a total distance equal to sum of a predetermined distance between the container sensor and the label applicator plate in an advancing direction of the conveying unit and one-half of the diameter of the container.